Dual clutch mechanisms typically have a single input shaft that, through a pair of selectively engageable plate clutch mechanisms, drives one of a pair of output shafts for rotation. In some such arrangements, each of the input and output shafts are concentrically arranged with respect to each other. One example of such an arrangement uses an input shaft positioned within a hollow inner output shaft, which in turn is positioned within a hollow outer output shaft.
Such dual clutch mechanisms typically have a first clutch arrangement which has a driven side and a driving side, along with a second clutch arrangement which also has driven side and a driving side. The selective activation of either of the first and second clutch arrangements allows for the input shaft to drive one of the inner and outer output shafts. The driven sides of the first and second clutch arrangements is driven for rotation via the input shaft, which is disposed within both the inner and outer output shafts. The driving side of the first clutch arrangement selectively drives one of the inner and outer output shafts for rotation, while the driving side of the second clutch arrangement selective drives the other of the inner and outer output shafts for rotation.
Dual clutch mechanisms can be used in automotive transmission systems, such as for use with shifting between gears in an automatic transmission. A consideration in configuring a dual clutch mechanism for a particular automobile can be the size of the mechanism, and in particular the overall radial extent of the mechanism.
Having concentric input, inner output and outer output shafts restricts the minimum radial extent available for a given dual clutch mechanism. The minimum radial spacing taken upon the three concentric shafts is further limited by operational requirements for each of the shafts. The desired properties of the three shafts also are restricted by the minimum overall radial space available for the dual clutch mechanism. Morever, the longer the axial lengths of the shafts, generally the less torsionally stiff the shafts, which represents a further limitation in the design of dual clutch mechanisms.
A clutch support is often provided concentric with the input and output shafts for transmitting rotation from the input shaft to the driven sides of both of the first and second clutch mechanisms. The clutch support partially surrounds the outer output shaft, which in turn surrounds the inner output shaft, and which itself surrounds the input shaft. Sealing rings are positioned between the clutch support and the adjacent shaft or an intermediate fluid distribution sleeve.
The clutch support is often connected to the input shaft by a clutch housing, which can extend from one side of the clutch mechanism, adjacent the input shaft, to the other side of the clutch mechanism, adjacent the output shafts. In such a clutch mechanism, the driving force is transmitted from the input shaft to the housing, which wraps around the first and second clutch arrangements from one side to the other, to the clutch support and then finally to the driven sides of the first and second clutch mechanisms. Such a driving path can result in undesirably high stresses in the transmission housing. The high stresses in the transmission housing can be exacerbated as the radial extent of the dual clutch mechanism is increased.
In addition, having a concentric clutch support, outer output shaft, inner output shaft and input shaft requires a minimum radius, depending upon the sizes of the support and shafts due to the diameters of each. This minimum radius is a limitation on the overall radial extent of the dual clutch mechanism. This minimum radius is also a limitation on the minimum diameter of sealing rings necessary to seal between the clutch support and the adjacent inner output shaft or an intermediate fluid distribution sleeve.
Dual clutch mechanisms often have radially extending pistons for selectively activating the first and second clutch mechanisms. The first and second clutch arrangements can be radially spaced from the input and output shafts. In such cases, the pistons extend radially from proximate the clutch support to clutch plates of each of the first and second clutch mechanisms. The larger the radial extent of the dual clutch mechanism, the greater the force that can be required to engage the piston with its respective plate clutch arrangement.
Dual clutch mechanisms can have the first and second clutch arrangements positioned parallel to each other along the principle axis of rotation of the clutch mechanism. An example of a parallel dual clutch mechanism is disclosed in EP1195537. As shown in the '537 publication, however, the input shaft is concentrically disposed relative to both a hollow inner and a hollow outer output shaft.
Dual clutch arrangements also can have the first and second clutch mechanisms positioned radially with respect to each other. An example of a radial dual clutch mechanism is disclosed in U.S. Pat. No. 6,491,149. As shown in the '149 patent, however, the input shaft is concentrically disposed relative to both a hollow inner and a hollow outer output shaft.